It was revealed that limited experimental data existed regarding the conditions of epilayer thickness and composition under which dislocation-dislocation interactions affected strain relaxation. Ultra-high vacuum transmission electron microscopy was used here for the direct real-time observation of dislocation interactions. The microscope was equipped with in situ chemical vapour deposition capabilities which permitted the imaging of dislocation motion during the growth and annealing of SiGe/Si(001) heterostructures. This permitted the efficient determination of the regimes of epilayer thickness and composition within which dislocation interactions arrested the forward motion of a threading dislocation segment. For the lowest thicknesses and compositions, all of the dislocation interactions caused the threading segment to become blocked. Above a certain value of thickness and composition, dislocation motion was halted only when the 2 dislocations had parallel Burgers vectors. This was due to a particular reaction, between dislocations, which occurred at their intersection. A quantitative analysis of the dynamic motion of threading dislocations, while in the presence of the stress field of the interfacial segment, permitted the estimation of the magnitude of the long-range interaction stresses. The latter increased as the net excess stress in the epilayer increased, and the interaction stresses were much greater when the Burgers vectors were parallel. Additional experiments indicated that dislocations, which became blocked during annealing, formed relatively stable configurations. Following a blocking event, a force which was greater than that associated with long-range interactions between dislocations was required in order to release the dislocations from their blocked configuration. This contradicted theoretical models, which instead predicted that the long-range interaction force alone controlled release.

In situ Transmission Electron Microscopy Studies of the Interaction between Dislocations in Strained SiGe/Si(001) Heterostructures. E.A.Stach, R.Hull, R.M.Tromp, F.M.Ross, M.C.Reuter, J.C.Bean: Philosophical Magazine A, 2000, 80[9], 2159-200